Adolescent girls and young women (AGYW) in southern Africa suffer some of the highest risks of HIV infection anywhere in the world. Without reduced incidence in this group, there can be no prospect of epidemic control and the HIV epidemic in high-burden countries will be perpetuated into successive generations. Efficacious prevention methods are now available (including pre-exposure prophylaxis [PrEP], condoms and voluntary medical male circumcision [VMMC] for male partners) but use is low. We hypothesize that the reason why use is low is related to factors acting at individual (preferences and biases), community (peer pressure and social norms) and logistical levels (nature of availability of services); and that interventions that address these barriers will help unlock the potential prevention impact of existing methods. But how these factors interact, and are best addressed with interventions, is poorly understood. This research will address this need to understand the multi-level influences on use of HIV prevention in AGYW and male partners, and will develop new prevention interventions by combining promising approaches from behavioral economics, community psychology, and mathematical modelling. The specific aims are to: 1) use the novel framework of HIV prevention cascades to identify drivers of risks and bottlenecks in HIV prevention for AGYW; 2) use small-scale randomized experiments to pre-test the impact, feasibility, acceptability and cost of behavioral economics and community psychology interventions to strengthen HIV prevention; and 3) estimate the population-level impact and cost-effectiveness if interventions were scaled-up. A household survey will be conducted in 8 sites in east Zimbabwe, covering all AGYW (15-24) and their potential male partners (15-29) and a sub-sample of older people. Questions will cover socio-demographic characteristics, sexual behavior, HIV risk perception, and attitudes towards and perceived availability, uptake and adherence to HIV prevention methods; and tests for HIV and HSV-2 infections will be done. Risk, time and social preferences; risk perception; and cognitive biases will be measured using experimental methods and real rewards, to move beyond self-reported data, and validated using data on HSV-2 and HIV incidence collected after 12 months follow-up. In each site, villages will be randomized into intervention and control villages. In intervention villages, HIV-negative AGYW will participate in feedback-based interactive counselling sessions to increase PrEP uptake by correcting misperceptions of HIV risks and availability, usability and efficacy of PrEP. Uncircumcised HIV-negative young men will receive a counselling session on VMMC by a circumcised young male health worker and further randomized into groups receiving different financial/material rewards for taking up VMMC. Intervention and control participants will be followed-up after 6 months to measure uptake of PrEP (using ARV diagnostics) and VMMC. Both intervention and control AGYW on PrEP will be randomized to a PrEP adherence intervention with personalized short text messages. All AGYW and young men will be followed-up again after 6 months (12 months in total) to measure HIV and HSV-2 incidence and PrEP adherence in AGYW. All data will be used in mathematical models of HIV transmission and HIV prevention cascades to identify bottlenecks in HIV prevention, and assess the population-level impact and cost-effectiveness of the pre-tested interventions. This research will also contribute to the evaluation of the DREAMS program in Zimbabwe.